I still really don't understand what an initializer does. please help me.

Great question!

Initializers are functions you create in a class that allow you to create an instance of an object in one or more ways. Without them you can't create an instance of that class.

Imagine someone is building you a home. This builder brings you a list of items he needs to complete the construction of your home. If you bring him all these items he'll be able to build you a nice home. In the same way when you fill out an initializer you're providing your class the things it needs to create an instance of that class.

Now imagine the same home above but someone else started building it and then abandoned it. Now you hire a builder to complete the home but this time you don't need all of the items as above because it's already halfway built. That's similar to creating another initializer that can create the same object but requires more or less variables to create an instance of a class.

Take a look at the code below to see an example of a Person class with 3 different initializers being used.

//: Playground - noun: a place where people can play

import UIKit

class Person {
  //Person attributes initialized to blank values to avoid nil
  var name = ""
  var age = ""
  var favoriteColor = ""

  //Default initializer
  init() {
    name = "John Smith"
    age = "24"
    favoriteColor = "Red"
  }

  //Initializer with name and age options
  init(name: String, age: String) {
    self.name = name
    self.age = age
    favoriteColor = "Red"
  }

  //Initializer with name, age, and favoriteColor options
  init(name: String, age: String, favoriteColor: String) {
    self.name = name
    self.age = age
    self.favoriteColor = favoriteColor
  }
}

//Default Initializer
var stranger = Person()

//Initializer with name and age options
var neighbor = Person(name: "Helga Ortiz", age: "33")

//Initializer with name, age, and favoriteColor options
var bestFriend = Person(name: "Seth Banks", age: "27", favoriteColor: "Purple")

The above example illustrates how one class can have multiple initializers. You can see each one gives me different options to create the class. This is useful because I don't always want to initialize every variable of a class and other times I want to be very specific.

I hope this helps. Initializers were one of the more complicated parts of Swift when it was introduced so it's not uncommon to feel confused about this. Just remember StackOverflow is your best friend as a developer :)